Proscenium Curtain Specifications define the material composition, construction, and operational requirements for fire curtains separating the stage from the auditorium in assembly occupancies. These specifications are critical components of stage-fire-safety-construction and are detailed in Chapter 41 of the 1935-Miami-Dade-Building-Code_p265_284.
Material Requirements
Proscenium curtains for Group A and B buildings must be made of incombustible materials capable of intercepting hot gases, flame, and smoke, preventing glow on the auditorium side for at least five minutes (p. 277). For stage openings not exceeding 60 feet in width, the curtain must consist of one thickness of asbestos cloth weighing at least 3¼ pounds per square yard (p. 278). The asbestos yarn must be reinforced with monel metal, nickel, brass, or similar alloys to maintain strength at temperatures up to 1700°F (p. 278). The cloth may contain up to 20% combustible fiber, but the total carbon content must not exceed 10% (p. 278). Both sides of the curtain must be painted with a mineral paint having a silicate of soda binder to ensure no light or smoke passes through (p. 278).
Construction and Design
The curtain is constructed from continuous strips of asbestos cloth with seams overlapping at least 1 inch and sewed with double rows of asbestos thread (p. 278). It must extend into steel smoke grooves on each side of the proscenium opening by at least 8 inches and overlap the top of the opening by 12 inches (p. 278). Steel pipe battens are sewn into the top and bottom of the curtain to provide weight and structure; the bottom batten must be at least 2½ inches in diameter for openings over 40 feet wide (p. 278-279). Roller grips are riveted to the side hem to hold the curtain in structural steel guides (p. 279). A yielding pad of incombustible material at least 3 inches thick is attached to the bottom to form a seal against the floor (p. 279).
Operating Equipment
The curtain is supported by flexible steel cables passing through sheaves in the gridiron to counter-weights (p. 279). At least six safety stop chains are attached to the top batten and the proscenium wall to support the curtain if the primary cables fail (p. 279). The operating mechanism allows for manual, hydraulic, or electric opening, but emergency closing must be by gravity via counter-weights (p. 280). An automatic control line with fusible links rated at 160°F allows the curtain to lower itself automatically in case of fire (p. 280). Smoke grooves on the sides must be made of structural steel plates at least ¼ inch thick, 12 inches deep, and 6 inches wide (p. 280).
Testing and Approval
Every proscenium curtain installation must undergo operating tests and be approved by the building-inspector before the theater can open to the public (p. 280). New designs not obviously superior to the specified standards must pass a standard fire test for five minutes without glowing or passing smoke or flame (p. 280-281). These requirements ensure compliance with fire-resistive-construction-requirements and protect occupants in group-a-occupancy-requirements.
Related Concepts
- stage-fire-safety-construction
- fire-resistive-construction-requirements
- group-a-occupancy-requirements
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- national-board-of-fire-underwriters
- american-society-of-mechanical-engineers